1. Field of the Invention
The present invention relates to a fuse including: a fuse element in which a pair of connecting terminals and a fusible body to connect electrically the pair of connecting terminals are integrally formed; and a chip-shaped metallic piece with low fusing point for adjusting the fusing characteristic of the fusible body, wherein the metallic piece is attached to the fuse element.
2. Related Art
In Japanese Examined Utility Model Publication No. 3-13960 or Japanese Unexamined Patent Publication No. 7-14494, there is disclosed a fuse of large electrical capacity in which a mass of metal of low fusing point such as tin or lead is held in the middle in the longitudinal direction of a fusible body which forms a fuse element, and the fusing characteristic of the fuse is improved by alloy generated by the diffusion of the metal of low fusing point.
FIG. 4 is a perspective view showing an example of the conventional fuse which is similar to the fuse disclosed in the above utility model and patent publications.
The fuse 1 shown here is a fusible link, which is attached to an insulating housing not shown in the drawing. This fuse 1 includes: terminal connecting portions 3, 3 formed at both ends; and a belt-shaped fusible body 5 to connect electrically the terminal connecting portions 3, 3 with each other, wherein the terminal connecting portions 3, 3 and the belt-shaped fusible body 5 are integrally formed by means of press forming.
In this connection, both ends of the connecting terminal portions 3, 3 are curved inside. Accordingly, on the fore end side of the connecting terminal, that is, at the lower portion of the connecting terminal in the drawing, there is formed an electrical contacting portion S with which a tongue-shaped male connecting terminal is engaged and connected.
The fusible body 5 is composed in such a manner that a pair of narrow leg pieces 5a, 5a continued to the connecting terminal portions 3, 3 are connected with each other and that a chip-shaped metallic mass 8 of low fusing point, which is lower than the fusing point of the fusible body 5, is attached to the intermediate portion in the longitudinal direction of the connecting terminal portions by a pair of calking pieces 7. In this connection, the calking pieces 7 are formed in such a manner that they extend in the width direction of the fusible body 5. When the calking pieces 7 are calked being curved round the metallic mass 8 of low temperature, they can be pressured and fixed to the fusible body 5.
The fuse 1 composed as described above is attached to an electrical circuit via the electrical contacting portion S. When a voltage is impressed between the terminal connecting portions 3, 3, the fuse element 2 is energized with electric current. Then, as shown in FIG. 5, the metallic mass 8 of low fusing point diffuses in the fuse element 2, so that an alloy layer 9 is formed on the fusible body 5 side. Since the specific resistance of the alloy layer 9 is higher than the specific resistances of the metallic mass 8 of low temperature and the fuse element 2, Joule's heat is generated on the alloy layer 9 at this time. Therefore, the fuse element 2 is fused off by the influence of Joule's heat.
In this connection, since diffusion of metal proceeds to the direction of gravity, a contact surface of the metallic mass 8 of low fusing point with the fuse element 2, that is, a surface on which the alloy layer 9 is formed remarkably appears in one direction which corresponds to the direction of fuse setting.
Accordingly, when the fuse setting direction is changed variously being restricted by the space in an actual vehicle when the fuse is incorporated into the vehicle, that is, when the fuse setting direction is set laterally or reversely, the fusion characteristic of the fuse is varied, that is, when the fuse setting direction is set laterally or reversely, the fusing time is extended.